The superoxide anion (O2-) and the myeloperoxidase-halide-hydrogen peroxide enzyme systems play a major role in the microbicidal activity of phagocytic cells. The generation of toxic byproducts such as singlet oxygen (1O2) and hydroxyl radicals (OH.) by these systems may contribute to their antimicrobial effect. Basophils and mast cells (both human and rat) generate O2- simultaneously with histamine release after either immunologic or non-immunologic stimulation. Objectives of this research grant include: 1) characterization of the peroxidase obtained from secretory granules (with intact perigranular membranes) of rat peritoneal mast cells (RPMC). The effectiveness of various halides, the pH optimum, and influence of various peroxidase inhibitors on the antimicrobial activity of this peroxidase when combined with H2O2 will be studied. This system will be tested for chemiluminescence and 1O2 formation (by conversion of 2,5 diphenylfuran (DPF) to its specific 1O2 product cis-dibenzoylethylene (cis-DBE). 2) to determine what the consequences of O2- generation are in RPMC; formation of 1O2 (measured by conversion of DPF to cis-DBE) and OH. (measured by production of either ethylene from either methional or sodium alpha keto-gamma-methiolbutyrate) will be examined after immunologic (anti-IgE) or non-immunologic (48/80, ionophore A23187) stimulation of these intact cells. If 1O2 and Oh formation are found, then granule fractions of the RPMC will be examined for 1O2 and OH production. Cytochemical studies will be attempted to locate by electron microscopic techniques the oxidase required for O2 - generation and the peroxidase of RPMC. 3) to determine the biologic role of O2- and peroxidase in immediate hypersensitivity reactions, 3 areas of clinical relevance will be studied. The effect of the mast cell peroxidase inactivation of slow-reacting substance of anaphylaxis will be examined. Mast cells adhere to Schistosoma mansoni via a C3 receptor and preliminary observations indicate histamine release and O2- production consequent to this interaction. Possible involvement of the peroxidase system and generation of 1O2 and OH. during this interaction will be studied. The role of O2- generation in the late phase of the immediate IgE-dependent wheal and flare reaction will be determined by compar (Text Truncated -Exceeds Capacity)